Technical Abstract:
Poultry meat and eggs provide one of the most important meat sources for the world. To meet the growing demand of consumers, the poultry industry has become more consolidated and chicken rearing more concentrated to enhance efficiency. While this allows for more economical meat and egg production, it has the unfortunate consequence that disease outbreaks occur more frequently and with greater severity. Genetic resistance to disease is attractive as breeders have been exploiting genes for disease resistance for years, even with limited knowledge about the genetic or molecular basis of such phenotypes. The advent of modern molecular genetics has raised the promise that genes conferring disease resistance can be identified and elite strains with high disease resistance selected based on molecular markers, which has been demonstrated in other species. This chapter reviews the current methods used to identify resistance genes for specific diseases in chickens. Genetic resistance to the majority of diseases is usually complex or controlled by many genes as well as influenced by environmental conditions. Thus, the candidate gene approach and genome-wide quantitative trait loci scans will be discussed in detail. Also shown is how the new techniques of DNA microarrays (global gene expression) and two- hybrid (protein interaction) screens can be integrated with genetic studies to reveal positional candidate genes for QTL.